1691891621722 has 4 divisors (see below), whose sum is σ = 2537837432586. Its totient is φ = 845945810860.

The previous prime is 1691891621701. The next prime is 1691891621729. The reversal of 1691891621722 is 2271261981961.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 1668537974961 + 23353646761 = 1291719^2 + 152819^2 .

It is not an unprimeable number, because it can be changed into a prime (1691891621729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 422972905429 + ... + 422972905432.

Almost surely, 2^{1691891621722} is an apocalyptic number.

1691891621722 is a deficient number, since it is larger than the sum of its proper divisors (845945810864).

1691891621722 is an equidigital number, since it uses as much as digits as its factorization.

1691891621722 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 845945810863.

The product of its digits is 1306368, while the sum is 55.

The spelling of 1691891621722 in words is "one trillion, six hundred ninety-one billion, eight hundred ninety-one million, six hundred twenty-one thousand, seven hundred twenty-two".